The leaf and stem mines of British flies and other insects
 

(Coleoptera, Diptera, Hymenoptera and Lepidoptera)

by Brian Pitkin, Willem Ellis, Colin Plant and Rob Edmunds

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INTRODUCTION

The larvae of many flies (Diptera), moths (Lepidoptera), sawflies (Hymenoptera) and beetles (Coleoptera) feed within the leaves and stems of plants. As they feed and grow, the larvae move through their host plant's tissues, often creating characteristic mines.

A knowledge of a mining insect's host preferences coupled with the often diagnostic features of the mine and the lifestyle and form of the immature stages of the miner enable many species with known hosts to be identified, frequently more readily than the insect itself. Such is the state of our present knowledge, however, that adults should be reared whenever possible to be certain of their identity and to confirm the miner/host plant association.

A total of 885 insects are recorded as miners in Britain and Ireland. More than 1,100 species are discussed here, although not all are miners as all agromyzids recorded in Britain and Ireland whether miner or not are included. The majority of miners are moths in the families Acrolepiidae, Alucitidae, Batrachedridae, Bedelliidae, Bucculatricidae, Coleophoridae, Cosmopterigidae, Crambidae, Depressaridae, Epermenidae, Eriocraniidae, Gelechiidae, Gracillariidae, Glyphipterigidae, Heliozelidae, Incurvariidae, Lyonetiidae, Momphidae, Nepticulidae, Pterophoridae, Roeslerstammiidae, Tineidae, Tischeriidae, Tortricidae, Yponomeutidae, Ypsolophidae and Zygaenidae. The next largest group are flies in the families Agromyzidae, Anthomyiidae, Chironomidae, Dolichopodidae, Drosophilidae, Ephydridae, Psilidae, Scathophagidae, Sciaridae, Syrphidae, Tephritidae. The third largest group are beetles in the families Buprestidae, Chrysomelidae and Curculionidae. The smallest group are hymenopterous sawflies (Tenthredinidae).

Scope

This account of mines is concerned solely with British insects, although known host associations elsewhere are given.

The majority of Diptera mines can be readily distinguished from those of moths, sawflies and beetles. Diptera mining larvae typically cut a semi-circular exit through the leaf epidermis, whereas moth, sawfly and beetle larvae chew a hole. The larvae of diptera, often called maggots, also lack a head capsule and legs, but have a characteristic chitinised cephalo-pharyngeal skeleton.

The majority of British leaf- and stem-mining flies belong to the family Agromyzidae. The only comprehensive account of this family in Britain is that of Spencer (1972). Although this includes a checklist of the then known host plants by family and their miners, the diagnostic features of the mines if mentioned are only described within the species-oriented keys to adults. Moreover, since this account was published, further host plants have been confirmed or rejected; a number of species new to Britain have been recorded; and the systematics of the family has undergone considerable revision (see Spencer, 1990).

Not all of the species of Agromyzidae recorded in Britain are leaf- and/or stem-miners, some such as Agromyza erythrocephala, Phytomyxa wahlgreni, Melanagromyza cunctans and the three species of Hexomyza are gall-formers and Melanagromyza fabae is a root-feeder. Others, such as most other species of Melanagomyza, species of Phytobia and many others are stem-borers. In addition Gymnophytomyza heteroneura, Liriomyza lutea and eight species of Phytomyza are seed-feeders; and Phytomyza nigritula and Phytomya soenderupi are petiole miners. The lifestyle of 58 species of Agromyzidae is currently unknown and even when the lifestyle is known, the host plant may be unknown. For the sake of completeness, all British species of Agromyzidae are included here, whether or not they are leaf- or stem-miners and whether or not their host plant is known.

In addition to the species of Agromyzidae discussed here, this account covers the species of British insects which are or have been recorded as miners.

Scientific names of miners used here follow Fauna Europaea. Scientific and common names of host plants used here follow the Botanical Society of Britain & Ireland (BSBI) checklist.

Economic importance

The damage caused by some mining flies to crops and ornamental plants can be of economic significance. Several agromyzid pest species are recorded in Britain. The Cereal leaf miner, Agromyza nigrella (Rondani), is a serious pest of wheat; Agromyza nigrociliata Hendel is potentially a serious pest of cereals; the Tomato leaf miner, Liriomyza bryoniae (Kaltenbach), is a significant pest of several genera of cultivated plants; Napomyza cichorii Spencer was described as a serious pest of cultivated chicory in Belgium and the Netherlands; and the Cabbage leaf miner, Phytomyza rufipes Meigen, is a common pest of Brassica spp. In addiiton the anthomyiid Pegomyia betae is a notorious pest of beet.

In addition to these pests, three other polyphagous non-British species of agromyzid, Liriomyza huidobrensis Blanchard (the Vegetable leaf miner), Liriomyza sativae Blanchard and Liriomyza trifolii (Burgess) (American serpentine leaf miner), have been intercepted on ornamental and vegetable crops at their point of entry into Britain. Although they are not British, they are included in the lists and notes. All records on particular hosts are noted and summary lists of the recorded hosts world-wide by host plant family and genus are given.

The keys

Keys by host plant genus are provided for all known mines discussed, although some of the records require confirmation and some of the records are based on non-British associations. In addition links to keys for related genera are included. More than 14, 000 host plant or putative host plant associations are included, although only some 5, 000 of these are based on British records.

Access to the keys is provided by scientific and where possible by common name (only about 52% of the vascular plants recorded in Britain have common names). Many of the miner/host associations are based on host genera only.

An additional key is provided to the species of Liriomyza recorded in glasshouses and/or quarantine interceptions.

Reliability of fly/host associations

Unfortunately host records in the literature are frequently ambiguous, it is assumed for the purposes of this account that records in local faunas (e, g, Stubbs & Chandler, 1978; Robbins, 1983, 1989 and 1991) refer to British records, unless stated to the contrary, although this may not necessarily be the case.

Some published records are considered here to be erroneous due to either misidentification of the host or the miner. Such errors are noted in text. Host insect/host associations cited here from the literature can be considered most reliable if represented by voucher specimens of both the mines and reared adults, as is sometimes the case in The Natural History Museum's collection (which includes the important collections of leaf- and stem-mines of Emmett, Griffiths, Hering, Spencer & Parmenter).

Notes on species

A single page is devoted to each species of insect. Where known the lifestyle of all included species is given along with a description of the mine and diagnostic characters of the larva and puparium; the host preferences in Britain and elsewhere; the time of year when mines (or larvae) and adults may be found in Britain; and the known distribution in the British Isles and elsewhere.

Images

More than 2, 800 images of mines, larvae, larval cases, puparia and adults are included. As far as possible these images are of freshly collected material.

Images of 326 host plants have also been included. Links to images of host plant species in British Wild Flowers by John Somerville et al. are also provided.

All images are the copyright of the relevant photographer.

Parasitoids

By far the most important mortality factor are parasitoides. Very commonly, when opening a mine, one can encounter a parastoid larva that is sucking the liquified body contents of its host. It is impressive to see how an, often quite small, parasitoid, has overpowered its victim that is almost motionless and has its body colour and transparancy totally altered (Ellis in Bladmineerders en plantengallen van Europa).

Several hundred species of British and Irish Hymenoptera parasitoids have been recorded on British and Irish miners and these are included in lists by superfamily and family and on relevant species pages.



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Last updated 24-Aug-2016  Brian Pitkin Top of page